TOKYO – Sullied by a bout-fixing scandal, allegations of tax evasion and a storm of criticism over bad conduct, sumo's bad boy star Asashoryu left Japan on Wednesday to seek treatment in his native Mongolia for a stress disorder.

Sumo stars hold a special place in the hearts of the Japanese, and Asashoryu's problems have been the top story in Japan for most of the summer. He was followed to the airport by dozens of reporters and cameramen.

One national TV network showed the menu he would be fed on the flight, and even Prime Minister Shinzo Abe expressed his concern.

“I hope Asashoryu can concentrate on his treatment back home and stage a speedy recovery,” Abe told reporters Wednesday.

Asashoryu, who is 26 and has won 21 tournament titles, holds the highest rank in the ancient sport. However, last month he was slapped with a two-tournament ban and a pay cut, one of the harshest punishments ever meted out to a grand champion, for playing in a charity soccer match in Ulan Bator after bowing out of an exhibition tournament in Japan. He claimed he was injured.

His trainer, Takasago, said the wrestler was so devastated by the punishment that he holed himself up in his room and has shown signs of a serious stress disorder. He hasn't talked to the media since.

Expectations, both in and out of the ring, are high for sumo champions.

Like all wrestlers, grand champions are expected to wear kimono when they appear in public, to keep their hair in a well-oiled topknot and to avoid controversy. But grand champions, called yokozuna, are expected to set an even more demanding example of humility and devotion to the sport.

Asashoryu, despite being the most successful wrestler currently in the ring, has had trouble keeping up his image.

This week, allegations arose that he underreported his taxes.

In January, he was accused of being involved in a bout-rigging scandal by a tabloid-style weekly magazine. While the JSA investigated and determined there was no wrongdoing on his part, the damage to his reputation was significant.

He also was involved in a hair-pulling episode earlier in his career when he yanked the topknot of fellow Mongolian Kyokushuzan during a bout. Hair-pulling in sumo is akin to ear-biting in boxing, and never before had a grand champion lost a bout for resorting to it.

Sumo currently has only two grand champions. The other, Hakuho, is also from Mongolia.